SPECTROSCOPIC STUDIES OF POLYMORPHS OF ALPO4 AND SIO2

IR spectra of basic polymorphic forms of AlPO4, measured at different temperatures, are presented. Diffuse reflectance spectroscopy has been used for high temperature measurements. According to the crystal stru ctures of different AlPO4 forms by means of factor group analysis, a n umber of modes and their activities have been determined. An attempt t o assign bands to specific normal vibrational modes has been undertake n, comparing spectra of subsequent forms of AlPO4 with each other. The obtained results have been discussed with regard to data referring to various isomorphous polymorphic forms of SiO2, comparing, respectivel y, cristobalite with phosphocristobalite, berlinite with quartz, and p hosphotridymite with tridymite (M. Handke and W. Mozgawa, Vib. Spectro sc. 5 (1993) 75; M. Handke, W. Mozgawa and M. Rokita, Michrochim. Acta [Suppl] 14 (1997) 511). Differences and similarities have been shown for the spectroscopic data and thus for structures of AlPO4 and SiO2. (C) 1998 Elsevier Science B.V. All rights reserved.